Thermal energy conversion

ABSTRACT

A system is disclosed for converting thermal energy into chemical energy by means of a low-temperature process. A liquid flow loop with two vertical columns that are interconnected at the top and bottom circulates an electrically conducting fluid, such as mercury. A convective flow of this electrically conducting fluid is established by heating the fluid in one of the columns and cooling the fluid in the other column to establish a weight differential between the fluid in the two columns. A magnetohydroynamic generator is placed on this loop so that, as the fluid flows through the loop and through the generator, electrical energy is generated. This electrical energy is used to electrolize a second fluid, such as a solution of sulphuric acid, into gasses such as hydrogen and oxygen. The gasses so generated are injected into the rising column of the electrically conducting fluid to increase the weight differential between the fluid in the two columns and enhance the convective flow of that fluid. These gasses, which contain chemical energy, are then removed from the loop at the top of this column.

BACKGROUND OF THE INVENTION

With the advent of higher prices for the energy the world consumes, muchinterest has been generated in new sources of energy and in moreefficient uses of this energy. One of the energy conversion devices forwhich promise has been held is the magnetohydrodynamic generator (MHD).The basis for the operation of an MHD is that passing an electricallyconducting fluid through a strong magnetic field will produce anelectric potential between opposite sides of the throat through whichthe conducting fluid flows. The magnitude of the power generated with agiven fluid is proportional to the velocity of the fluid through thethroat.

MHD development has typically focused on the use of high temperature,high pressure gas or plasma, although some systems have been developedusing an electrically conducting liquid. The temperature of the plasmaor liquid used in these devices is usually on the order of severalhundred to a few thousand degrees Celsius. The pressure under which theworking fluid operates is also very high in most systems, on the orderof several hundred to a few thousand pounds per square inch. The use ofsuch high temperature and pressure fluids limits the choice of materialsout of which the system can be made. The high temperatures and highpressures in these systems also make the systems prone to leaks andcontribute to the rapid deterioration of machinery such as pumps used inthe system.

To provide the flow of conducting fluid through the MHD throat, somesystems have incorporated means for establishing a convective flow ofthe fluid around a closed loop. This convective flow is established byheating the fluid at one point in the loop and cooling it at another.Such a system is shown in U.S. Pat. No. 3,375,664 to Wells. It has beenfound, though, that the low velocity thus obtained has not beensufficient to permit the MHD to generate more than a few milliwatts ofpower even with vertical leg members up to 100 feet tall. Another meansof causing a flow of the conducting fluid through an MHD loop has beento establish a convective flow by introducing a gas into part of theloop to create a density differential between the fluid in differentsections of the loop. This has typically been accomplished by boilingeither the conducting liquid or a second fluid and using the vaporbubbles to leviate one column of the fluid. A system that operates inthis manner is disclosed in U.S. Pat. No. 3,443,129 to Hammitt. Suchsystems, however, have been troublesome, since boiling the fluid takesthermal energy from the system, reducing the heat in the conductingfluid in the rising column. Also, the height and temperature of therising column are severely constrained by the need to preventcondensation of the gas bubbles before they reach the top of the column.

SUMMARY OF THE INVENTION

The present invention efficiently converts thermal energy (heat) into analternate form of energy by means of a low-temperature process. Theinvention consists of a fluid flow loop with two vertical columnsinterconnected at the top and the bottom. The fluid that flows in thisloop is an electrically conducting fluid, preferably a liquid such asmercury. The column in which the fluid rises is heated to a temperatureof approximately 40°-150° C. by a thermal source and the column in whichthe fluid flows down is cooled to a temperature of approximately 0°-30°C. by means of a lower temperature heat sink. The difference in thedensity of the fluid in these columns induces a convective flow of thatfluid through the loop. An MHD is coupled to one of these verticalcolumns. The MHD includes a magnet that creates a strong magnetic fieldperpendicular to the flow of the fluid. As the fluid flows throughthroat sections that have electrodes in contact with the fluid, anelectric potential is generated between the electrodes, causing anelectric current to flow through the electrodes and through an externalelectric circuit, from which power may be drawn. The key to the presentinvention is that the electric power so produced is largely fed back toaugment, or speed up, the flow of the conducting liquid. This isaccomplished by using the electric power to dissociate water moleculesin an electrolytic solution, such as sulfuric acid, H₂ SO₄, and injectsome or all of the gasses obtained (H₂ and O₂) into the rising column ofconducting liquid. The gas is removed from the loop at the top of therising column and may be put to any of a number of uses. The remainderof the gases, which are not injected into the loop may be taken directlyfrom the electrolysis and put to use. Among the possible uses for thegasses produced by this system are burning to produce heat, power andpure water using them to synthesize other fuels, such as methane ormethanol. The introduction of the gas into the rising column greatlyreduces the density and weight of the rising column of electricallyconducting liquid, and hence increases the weight difference between thetwo columns of liquid. As the weight difference between the columns isincreased, the convective flow of the liquid is increased, furtherincreasing the production of electrical energy. With the increasedelectrical output, more gasses are produced, and the convective flowvelocity of the liquid is further increased, which additionallyincreases the amount of electric power generated by the MHD. The rate ofgeneration of the electrolyzed gasses is increased until an equilibriumis established between the generation of the gasses and the viscous andother flow retarding forces.

The Thermal Energy Conversion System of the present invention hasnumerous advantages over the MHD systems previously developed. Theseadvantages include:

(1) lower operating temperatures for the working fluid;

(2) lower pressures in the system loop;

(3) less severe constraints on the design and size of the systemcomponents;

(4) less severe constraints on the choice of materials out of which thesystemn components are made; and

(5) greater power output with a smaller system due to increasedoperating efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of the Thermal Energy Conversion System ofthe present invention.

FIG. 2 is a perspective view of the magnetohydrodynamic generatorcoupled to the fluid flow loop.

FIG. 3 is a perspective view of the magnetohydrodynamic generator withthe magnet withdrawn from the throat section of the fluid flow loop.

FIG. 4 is a cross-sectional view of the magnetohydrodynamic generatorused in the present invention taken along line 4--4 of FIG. 2.

FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 2.

FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 2.

FIG. 7 is a schematic drawing of a first alternative embodiment of theThermal Energy Conversion System.

FIG. 8 is a schematic drawing of a second alternative embodiment of theThermal Energy Conversion System.

DESCRIPTION OF THE PREFERRED EMBODIMENT General System

The system of the present invention is shown schematically in FIG. 1. Itcomprises a fluid loop 11 that is preferably closed, including first andsecond vertical columns or legs 13 and 15 that are interconnected at thetop and bottom. A conducting fluid, such as liquid mercury, flowsthrough the loop 11. Liquid mercury is advantageous becaause of its highelectrical conductivity, high density, and low specific heat value, butother electrically conductive fluids such as electrolytic solutions mayalso be used, depending on cost considerations, equipment design oravailability, or other factors. On the second column 15 is an electricgenerator 101, such as a magnetohydrodynamic generator (MHD) 101.Electrical leads 43 transmit the electric potential generated by the MHD101.

A source of thermal energy 21 is coupled to the loop near the bottom ofthe first column 13. This source 21 may be virtually any type of thermalenergy source, including a burner for fossil fuels or a heat exchangerdrawing heat from a reservoir heated by either solar energy orgeothermal energy. The temperature increase provided by the thermalenergy source 21 depends upon the environment in which the systemoperates. This temperature increase can range from 20° to 100° C. ormore, and is preferably at least 40° C.

A heat exchanger 31 is connected to the loop near the top of the secondcolumn 15 to draw heat from the conducting fluid and transfer it to aheat sink, such as a large body of cool water that is isolated from thesun, or some other low temperature body, which may be a body of ice ifthe system is used in a particularly cold environment.

A gas injector 59 for introducing gas into the system loop is placednear the bottom of the first column 13. Gas injector 59 is a gas nozzleoutlet of conventional design and is substantially centrally located incolumn 13.

A gas separator 71 is coupled to the loop near the top of the first leg13. Separator 71 may be of conventional design for drawing gas from atwo-phase flow. Gas separator 71 permits the liquid mercury to continueflowing around the loop, while removing the gasses introduced by gasinjector 59 to be drawn off through outlet 73. Outlet 73 is connected sothat the gasses may be put to other uses, such as burned to produce heator power, stored to be burned later, or used to synthesize other fuels,such as methane or methanol.

An electrolytic gas generator 51 uses the electrical energy generated bythe MHD 101 to electrolyze an electrolyte, such as a solution ofsulfuric acid (H₂ SO₄) to generate hydrogen and oxygen gas, whichcontain chemical energy. The pressure at which the gas generator must becapable of producing the gasses depends upon the static prssure column13 at gas injector 59 caused by the column of mercury, since, to enterthe column, the gas must be at a pressure at least as great as that ofthat static pressure. This static pressure depends on the height of thecolumns 13 and 15. For a small system with short columns, the gasgenertor 51 need only produce the gas at a pressure of a few pounds persquare inch, while a gas generator coupled to a system using much tallercolumns needs to produce the gas at a pressure on the order of a fewhundred pounds per square inch.

Outlet 53 from the gas generator 51 is preferably designed to keep theoxygen and hydrogen formed by the gas generator separate, since togetherthey form a potentially exposive mixture. Outlet 53 branches into pipes55 and 57. Pipe 55 leads to gas injector 59, so that part or all of thegasses generated by the electrolytic gas generator 51 may be injectedinto the first column 13. Valve 63 is provided on pipe 55 to control thevolume of gas entering the fluid flow loop. Pipe 57 leads to a devicefor either storing or using the gasses. Advantageously, pipe 57 alsokeeps the gasses segregated, so that some of whichever of the gasses isinjected into the column 13 may, if desired, also be diverted away fromthe flow loop, and stored or used directly. Valve 65 on pipe 57 controlsthe volume of gas being diverted away from the flow loop. Adjusting thevalves 63 and 65 permits careful control of the portion of the gassesthat goes directly to other uses and the portion introduced into thefluid flow loop.

Electrical leads 43 and 47 permit the power generated by the MHD 101 tobe transferred to the electrolytic gas generator 51. This feedback ofthe power generated back into the system greatly increases the system'sefficiency. Leads 45 permit power that is not used to operate the gasgenerator 51 to be drawn off the system and used for other purposes.

The MHD

The MHD 101, shown in FIGS. 2-6, includes a magnet 111 with closelyjuxtaposed north and south poles 115 and 113, a nonferromagnetic block121, and electrodes 133 and 135. Between the poles 115 and 113 is athroat section 17 of the block 121 (FIG. 4). This throat section 17 isdefined by two closely juxtaposed rectangular walls 127 and 129 to allowa thin sheet of the mercury to pass between the poles of the magnet. Themagnetic poles 113 and 115 are closely juxtaposed to maximize theintensity of the magnetic field across the sheet of mercury passingthrough throat section 17. Block 121 further includes threaded openings122 and 124 for receiving the ends of the tubular piping that forms theremainder of the second column 15. The passage through which the mercurypasses is tapered within the portions of the block 121 above and belowthe throat section 17 to form a transition between the tubular sectionof the second leg 15 and the thin throat section 17. As shown in FIG. 2,the exterior of the block 121 is also narrowed at throat section 17 soit will fit between the poles 113 and 115 of the magnet 111.

Electrodes 133 and 135 (FIG. 5) are placed on either side of this throatsection 17 to tap the electric potential created between these two sidesof the throat section. These electrodes are advantageously shaped sothat continuous contact between the electrodes and the mercury flowingthrough the throat section 17 is promoted.

The throat section 17 is sized so that a venturi effect provides a ratioof approximately five to one between the speed of the mercury throughthe throat and the speed through the other sections of the loop.

The fluid flow passage through the MHD 101 must be constructed tocontain the mercury flowing through it, particularly at the threadedopenings 122 and 124, and at the points at which electrodes 133 and 135enter throat section 17. But the passage is not subjected to the veryhigh pressures that the MHD throat sections of systems that use a plasmaas the working fluid must contain.

The Electrolytic Gas Generator

Electrolysis occurs when an electric current is passed through anelectrolyte between two electrodes, an anode and a cathode. Ions in thesolution move to and from the anode and cathode so that material may betransported and deposited on one of the electrodes, new compounds may beformed, or gasses may be liberated. Certain electrolytes, such assulfuric acid, sodium hydroxide, and potassium carbonate, when dissolvedin water, cause the water itself to decompose into its component parts,hydrogen and oxygen, when a current is passed through the solution.

The amount of material or gas formed by the electrolysis can be foundusing Faraday's Laws, which say that (1) the amount of chemical changeproduced by an electric current is proportional to the quantity ofelectricity and (2) the amounts of different substances liberated by agiven quantity of electricity are proportional to their chemicalequivalent weights. (Equivalent weight=atomic weight divided by valencechange.) Thus, the amount of material or gas produced is proportional tothe current passed through the solution. When water is electrolyzed, thevolume of hydrogen and oxygen produced is proportional to the currentpassed through the solution.

An example of a simple electrolytic gas generator that may be installedin the present system as gas generator 51 is a fully charged automobilestorage battery comprising lead plates immersed in a solution ofsulfuric acid. As current is passed through the solution in the cell thewater in the solution is dissociated into hydrogen and oxygen. Thehydrogen is given off at one of the electrodes, and the oxygen at theother. As the electrolysis continues and the water in the electrolytesolution is dissociated into its component parts to form the gasses, thewater must be replaced, but the acid itself remains in the solution.

The gasses produced should be kept separate, since, in the case ofhydrogen and oxygen, the two gasses together form an explosive mixture.This separation can be maintained by placing a membrane between theelectrodes.

Since the amount of gas produced is proportional to the current, but notthe pressure under which the cell operates (except at the extremes), thegasses may be produced at relatively high pressures with negligibleincreases in the power consumed.

Other types of electrolytic cells may also be used as gas generator 51.A cell comprising a nickle anode and iron cathode immersed in a solutionof sodium hydroxide in water produces oxygen at the anode and hydrogenat the cathodes. Nickel electrodes immersed in a solution of potassiumcarbonate may also be used to produce hydrogen and oxygen.

The Thermal Energy Source

The thermal energy source 21 may be one of a number of availableapparatuses for transferring thermal energy to the fluid circulating inthe loop. The purpose of the thermal energy source 21 is to increase thetemperature of the liquid in column 13 relative to the liquid in column15 so that a density differential is established between the mercury inthe two columns, causing a convective flow of the fluid liquid aroundthe loop. Thus, the greater the temperature differential that can beestablished, the greater the convective flow of the liquid.

Particularly appropriate as a thermal energy source, in light of theinterest in renewable resources, is a heat exchanger drawing heat from asolar heated reservoir. Panels for heating liquids such as water usingsolar energy are commercially available in many sizes from numeroussources, as are containers for storing the solar heated water. Heatexchangers are also readily available that can be coupled to the closedloop and are suitable for circulating the heated water from thereservoir and transferring its heat to the mercury circulating in theclosed loop. Such apparatus can provide a 40° temperature differential,which is suitable for operation of the system.

Also appropriate would be the use of a heat exchanger circulatinggeothermally heated water. Geothermally heated water often is at a muchhigher temperature than solar heated water would be, on the order of120°-180° C., and thus would be able to produce a greater temperaturedifferential between the mercury in column 13 and the merciry in column15. This increased temperature differential is advantageous in that thedensity differential between the mercury in the two columns is greater,and consequently the convective flow of the mercury is increased. But,the availability of geothermal energy is limited.

In addition to the sources of thermal energy just discussed, a fossilfuel burner of conventional design may be used as thermal energy source21 to directly heat the circulating mercury.

Since the important consideration for operation of the system is thetemperature differential between the liquid in the two columns 13 and15, heat exchanger 31 must be connected to a heat sink capable ofabsorbing from the liquid the heat transferred to it by thermal energysource 21. In a system located in a temperature climate, this is mosteffectively done by circulating in the heat exchanger cool water drawnfrom a large reservoir kept cool by isolating it from exposure to thesun. In a colder climate, a large body of ice may be used, which wouldpermit the temperature of the mercury to be reduced to 0° C., or perhapslower.

Operation of the System

In operation, thermal energy is added by heat source 21 to theconducting fluid in the first column 13 to lower the density of thefluid in that column, thereby inducing a convective flow of the mercury.The heat so introduced into the conducting fluid is removed by the heatexchanger 31 at the top of the second column 15 to ensure thecontinuation of the temperature differential (and the densitydifferential) between the mercury in the first and second columns. Asthe fluid flows downward in the second column, it flows through thethroat section 17 of the MHD 101 in a direction perpendicular to themagnetic field established by the magnet 111. This flow, by reason ofFaraday's Laws, creates an electric potential between the sides of thethroat section 17, which is tapped by the electrodes 133 and 135. Thispurely temperature-induced convective flow through the MHD will generatea very low power output. The power output is low due to the low velocityof the electrically conducting fluid through the MHD.

The electric potential is produced in the following manner: When a sheetof conducting material, e.g. mercury, is passed through a magnetic fieldthat is perpendicular to the direction in which the conducting materialis moving, an electric potential develops between points on the sheet ofconductive material that lie on an axis perpendicular to both thedirection of movement of the conductive sheet and the direction of themagnetic field.

As the conductive fluid flows with velocity v through the perpendicularmagnetic field B, a force is exerted on each charge carrier in a third,mutually perpendicular direction. This force F is given by the vectorequation:

    F=qv×B

in which q is the charge of each charge carrier. The electric fieldintensity (E) resulting from this force is given by the vector equation:

    E=F/q=v×B.

This electric field yields an electric potential between two sides ofthe channel through which the conductor flows. This potential is:

    E=∫E·dL=∫(v×B)·dL

in which L represents the width of the sheet of conductive fluid.

In the MHD loop, flow equilibrium is reached when the electromotiveforce so generated equals the force driving the fluid flow, thedifferences in the weight of the mercury in the two columns.

By using the electric power generated by the MHD 101 to electrolyze asecond fluid in gas generator 51 and introduce the gasses so generatedinto the rising first column 13, the efficiency of the system can begreatly increased due to the increased rate of flow of the electricallyconducting fluid through the MHD. When the gasses produced by theelectrolytic gas generator 51 are introduced into the first column 13,the density and weight of the mercury in that column is substantiallydecreased, which increases the density and weight differentials betweenthe fluid in the first column 13 and the fluid in the second column 15.This increased differential greatly enhances the convective flow of themercury around the loop, increasing the rate of flow of the conductivefluid through the throat 17 of the MHD section of the loop. As this flowthrough the throat section is increased, so is the power produced by theMHD. This increase continues until a new flow equilibrium is reached.

The gasses introduced into the loop, which contain chemical energy, areseparated from the conducting fluid at the top of the loop by the gasseparator 71 and may be put to any of a number of uses, as mentionedabove.

Each cycle of flow (once around the loop) extracts an amount of energyproportional to the weight difference between the two columns(represented by the equation E=dW×h, in which dW is the difference inweight and h is the height of the column). The amount of power that canbe obtained from the system depends upon the speed or time it takes tocomplete the stroke, i.e., the rate at which the work is done. Thus, thepower is given by the equation P=dW×v, in which v is the speed of thefluid flow.

As the system continues to operate, the MHD 101 may generate more powerthan is needed to operate the electrolytic gas generator 51. When thisoccurs, electrical leads 45 may be attached to an external load suitablefor using this excess power. Alternately, electrical leads 45 may beconnected to a battery to store the power for later use. Accordingly,the system may be advantageously used to convert the thermal energysupplied by thermal energy source 21 to both chemical energy in the formof gasses and electrical energy.

ALTERNATIVE EMBODIMENTS General System

Alternatively to using a single upflowing column 13 in the MHD loop 11,two or more columns 13a and 13b may be used, as shown in FIG. 7. In thisembodiment, one of the gasses produced by electrolytic gas generator 51,for example the oxygen may be injected into column 13a and the othergas, the hydrogen, may be injected into column 13b. In this way, boththe gasses produced may be used to supplement the convective flow, whilekeeping the gasses separate. Since both gasses produced by the gasgenerator are used, the utility of the feedback of the electrical energygenerated by the MHD 101 is enhanced. This embodiment requires at leasttwo gas separators 71a and 71b (one to separate each gas out of theflow), and a gas injector 59a and 59b for each column 13a and 13b.

The Electrolytic Gas Generator

As an alternative to using a liquid metal such as mercury in the MHDloop 11 and electrolyzing a separate electrolyte in gas generator 51, anelectrolyte may be circulated through the MHD loop 11' (FIG. 8) andpassed through electrolytic gas generator 51' so that the MHD workingfluid itself is electrolyzed. From gas generator 51' part or all of thegasses may be injected into the column 13'. Pipe 57' allows whatever ofthe gasses are not injected into column 13' to be diverted and putdirectly to use.

I claim:
 1. An apparatus for converting thermal energy into chemicalenergy, comprising:(1) a closed fluid loop through which flows anelectrically conducting liquid, said loop comprising:(a) a firstsubstantially vertical column; (b) a second substantially verticalcolumn; (c) interconnection means between the top of said first columnand the top of said second column; and (d) interconnection means betweenthe bottom of said first column and the bottom of said second column.(2) means for creating a temperature differential between the portionsof said liquid in each column by heating the portion of said liquid insaid first column and cooling the portion of said liquid in said secondcolumn to form a density differential in said liquid and establish aconvective flow of said liquid through said loop; (3) amagnetohydrodynamic generator coupled to said loop for generatingelectrical energy from said flowing liquid, the amount of electricalenergy generated being proportional to the velocity of the said liquid;and (4) means for supplementing said convective flow to increase theelectrical energy generated by said magnetohydrodynamic generator byincreasing the density differential between the liquid in each of saidcolumns, comprising:(a) an electrolytic gas generator coupled to saidmangetohydrodynamic generator for using at least a portion of saidelectrical energy to electrolyze a second liquid to form a gas, said gascontaining said chemical energy; (b) means for introducing a portion ofsaid gas into said first column to decrease the density of the portionof said liquid in said first column and increase the densitydifferential between the portions of said liquid in each column; and (c)means for removing said gas near the top of said first column.
 2. Theapparatus of claim 1, wherein said magnetohydrodynamic generatorcomprises:(1) a throat segment of said second vertical column throughwhich said liquid flows; (2) a magnet creating a magnetic fieldperpendicular to said flow of said liquid through said throat segment sothat as said liquid flows through said throat segment an electricpotential is created between two sides of said throat segment; and (3)electrodes coupled to said throat segment, said electrodes tapping saidelectric potential.
 3. The apparatus of claim 2, wherein said throatsegment is of smaller cross sectional area than another section of saidsecond vertical column to provide a venturi effect to said flow.
 4. Anapparatus for converting thermal energy into chemical energy,comprising:(1) a closed fluid loop through which flows an electricallyconducting liquid, said loop comprising:(a) a first substantiallyvertical column; (b) a second substantially vertical column; (c)interconnection means between the top of said first column and the topof said second column; and (d) interconnection means between the bottomof said first column and the bottom of said second column. (2) means forcreating a temperature differential between the portions of said liquidin each column by heating the portion of said liquid in said firstcolumn and cooling the portion of said liquid in said second column toform a density differential in said liquid and establish a convectiveflow of said liquid through said loop; (3) a magnetohydrodynamicgenerator coupled to said loop for generating electrical energy fromsaid flowing liquid, the amount of electrical energy generated beingproportional to the velocity of the said liquid; and (4) means forsupplementing said convective flow to increase the electrical energygenerated by said magnetohydrodynamic generator by increasing thedensity differential between the liquid in each of said columns,comprising:(a) an electrolytic gas generator coupled to saidmagnetohydrodynamic generator for using at least a portion of saidelectrical energy to electrolyze a portion of said conducting liquid toform a gas, said gas containing said chemical energy; (b) means forintroducing a portion of said gas into said first column to decrease thedensity of the portion of said liquid in said first column and increasethe density differential between the portions of said liquid in eachcolumn; and (c) means for removing said gas near the top of said firstcolumn.
 5. An apparatus for efficiently converting thermal energy intoan alternate form of energy, comprising:(1) A fluid conduit throughwhich flows a fluid, wherein said conduit comprises:(a) a first,substantially vertical, leg; (b) a second, substantially vertical, leg;(c) first communication means between the top of said first leg and thetop of said second leg; and (d) second communication means between thebottom of said first leg and the bottom of said second leg; (2) firstmeans for adding thermal energy to said fluid, to create a flow of saidfluid, wherein:(a) said fluid flows upward through said first leg; and(b) said fluid flows downwardly through said second leg; (3) secondmeans coupled to said conduit near the bottom of said second leg forgenerating electrical energy from said flowing fluid; (4) third meanscoupled to said second means for using at least a portion of saidelectrical energy to form a gas, said gas containing chemical energy;and (5) fourth means for introducing into said conduit at least aportion of the gas formed by said third means so that the rate of flowof said fluid is increased.
 6. The apparatus defined in claim 5wherein:(1) said third means for forming a gas is an electrolytic gasgenerator that electrolyzes a second fluid; and (2) said fourth meansfor using said gas comprises means coupled to said conduit and to saidthird means for introducing said gas into said first leg.
 7. Theapparatus defined in claim 5, wherein:(1) said fluid is anelectrolyte;(2) said third means for forming a gas is an electrolyticgas generator that electrolyzes a portion of said fluid; and (3) saidfourth means for using said gas comprises means coupled to said conduitfor introducing said gas into said first leg.
 8. The apparatus definedin claim 6 or 7, additionally comprising fifth means coupled to saidconduit for removing said gas from said conduit wherein said fifth meansis coupled to said conduit near the top of said first leg.
 9. Theapparatus defined in claim 5, additionally comprising means for removingsaid thermal energy from said fluid, wherein:(1) said first means foradding thermal energy is coupled to said conduit on said first leg; and(2) said means for removing thermal energy is coupled to said conduitnear top of said second leg.
 10. The apparatus defined in claim 9,wherein said means for removing said thermal energy comprises:(1) a heatexchanger coupled to said conduit; and (2) a heat sink interconnectedwith said heat exchanger, suitable for absorbing the heat removed fromsaid fluid by said heat exchanger.
 11. The apparatus defined in claim 5,wherein said first means for adding thermal energy comprises:(1) a heatexchanger coupled to said conduit near the bottom of said first leg; and(2) a heat source interconnected with said heat exchanger suitable forsupplying thermal energy to said heat exchanger.
 12. The apparatusdefined in claim 11, wherein:(1) said heat source comprises a quantityof a third fluid; and (2) said quantity of a third liquid is heated bysolar radiation.
 13. The apparatus defined in claim 5, wherein:(1) saidthird means for forming a gas is an electrolytic gas generator thatproduces one or more gasses; (2) said conduit additionally comprises athird, substantially vertical, leg in which said fluid flows upwardly;(3) said fourth means is suitable for introducing some of said gassesproduced by said gas generator into said first leg; and (4) said fourthmeans is suitable for introducing an additional portion of said gassesproduced by said gas generator into said third leg.